Detachable blade bit



June 19, 1962 E. G. BRIGGS 3,039,548

DETACHABLE BLADE BIT Filed Jan. ".50, 1958 W FIG-5 g I l IEMMETT G. lBFZlGGS [FIG 2 INVENTOR.

United States Patent 3,039,548 DETACIIABLE BLADE BIT Emmett G. Briggs, Odessa, Tex. (1660 Ave. G, Seminole, Tern), assignor of one-half to Wendell Cotfee, Lubbock, Tex.

Filed Jan. 39, 1958, Ser. No. 712,136 4 Claims. (Cl. 175412) This invention pertains to earth boring and more particularly to a drilling bit with detachable blades.

In earth boring tools, such as are used in drilling wells in the ground, it is desirable for numerous reasons to have detachable blades. Of necessity the blade of a drilling tool must be a cantilever. The method of attaching these various cantilever blades to the main holder presents a problem. The principal difficulty is that the drilling portion of the bit itself is subject to extremely high loads and which may vary immensely; i.e., when drilling, a piece of rock may chip off which causes the blade to flex and tend to vibrate. If it is not very securely held in the holder, it will chatter.

An object of this invention is to provide a suitable bit with removable blades.

Another object is to provide a detachable blade bit which is free of chatter.

Another object is to provide such a bit that is easy to remove the blades.

Further objects are to achieve the above with a bit which is sturdy, simple, reliable, and true, yet cheap and easy to manufacture.

The specific nature of the invention, as well as other objects, uses, and advantages thereof will clearly appear from the following description and from the accompanying drawing, in which:

FIG. 1 is a perspective of a bit in accordance with this invention.

FIG. 2 is a partial sectional line 2--2 on FIG. 3.

(FIG. 3 is a cross-sectional view taken on line 3--3 of FIG. 2.

FIG. 4 is a cross-sectional view taken on line 44 of FIG. 2.

FIG. 5 is an axial section of the collar taken on line 5-5 of FIG. 3.

As may be seen in the accompanying drawings, a detachable bit of this type is intended to be attached to the lower end of drill stem 10. The drill stern has internal threads 12. Pin 14 is screwed into these threads. The pin has three sections. The threaded section which mates with the threads 12, hexagonal section 16, and holding section 18 are the three sections. Coaxial bore 20 extends through the pin for the passage of drilling mud. Collar 22 surrounds and is coaxial with the pin. The collar has a portion 24 which has an axial hole of hexagonal cross-section in it, which mates with the hexagonal portion 16 of the pin. Shoulder 26 is at the extreme upper end of the collar and is in contact with a corresponding shoulder of the drill stem 10. The collar has a conic drive portion 28 on the end opposite shoulder 26. This conic drive portion has an internal bore of conicshape. Driving lugs 29 are also within the conic drive portion 28 on the lower end thereof. If the bit is to be driven in a clockwise direction as shown in FIG. 3, these lugs protrude as wedges from the conic surface of conic drive portion 28 in a counter-clockwise direction as shown. Therefore, detachable blade 30 will be driven by a wedge surface rather than by a surface normal to the clockwise rotational force.

The driving lugs 29 are integral with the collar 22. The driving face 31 is a surface generally parallel to the axis of the collar 22. The leading edge 33 is the edge view of the bit, taken on ice of the driving face which intersects and makes a smooth and regular shape into the conic surface of the conic drive portion 28. The trailing edge 35 is a continuation of a cylindrical portion between the hexagonal portion 24 and conic drive portion 28. The trailing edge 35 of the lug 29 is aligned with the generatrix of the cylindrical bore at that area. The trailing face is radial, -i.e., it lies in a plane which contains the axis.

FIG. 3 shows three imaginary lines, lines 50, 52, and 54. All of these lines lie in a plane normal to the axis of the stern. Line 50 is any radial line which intersects the surface 31. Line 52 is perpendicular to line 50. Line 54 is drawn tangential to the surface 31 at the point the surface intersects the radial line 59. Also shown are two angles, angle apha being between the lines 52 and 54, and the angle beta between the lines 50 and 54. It may be seen that the angles alpha and beta are complementary. Therefore, if angle beta may be said to be an angle between the surface 31 and any radius intersecting that surface; then angle alpha is the complement of that angle. The angle alpha of the wedge is less than the angle of friction for the materials involved; i.e., if for the materials used, at a 12 deg. inclination to the horizontal the metals would start sliding upon one another, an angle of less than 12 deg. would be used. In use the blade will be forced into a tight locking position. When the force upon the blade is released, it will not move relative to the collar and no chatter will take place.

The section 18 of the pin is the frustum of a cone, tapering with the imaginary apex upward as seen in FIG. 2. Near the lower end there is an annular groove 32.

Each detachable blade is a segment, one-third of a complete revolution in cross-section. The blade 30 itself has two portions-the drilling tooth portion 34- and the holding portion 36. As may be seen, the drilling teeth are on the drilling face 37 and are set at an angle. This particular feature is covered by my copending application for US. patent, Blade Type Well Drilling Bit, Ser. No. 693,999 filed November 1, 1957, now abandoned. Both the surfaces of the holding portion 36 are conic. The outside conic surface has a greater apex angle than the inner surface. An axial section of the holding portion 36, as seen in FIG. 2, is slightly wedged. The outside surface of holding portion 36 is correlative with and contacts the inside surface of collar portion 28. Likewise, the inside surface of the holding portions 36 is correlative with and contacts the surface of section 18 of the pin. Each holding portion 36 has a driven depression 38. This driven depression is correlative with and contacts the driving lug 29 of the collar so that the blade is rotated by the collar. This driven depression slopes back and in from a direction of the drilling face 37 to back face 42. As the depression is correlative with the lug 29, the angle of slope of the depression (i.e., the angle between the surface of the depression and an imaginary line at right angles to a radius lying in a plane normal to the axis) is less than the friction angle for the materials of the blade and collar. Likewise, on the inside surface of each bit, there is an annular flange 40 which is correlative with and contacts the groove 32 in the pin.

The holding portion 36 does not extend to the hexagonal portion 16 of the pin, but stops short of that area.

Tightening the pin into threads 12 pulls the blades upward or into the collar. This action is primarly by the annular groove 32 and flange 40, aided by the internal conic surfaces of the blades. The collar butts against the drill stem 10 at point 26 and holds the blades by the conic surfaces at portion 28. Thus the blade is firmly held in an axial direction. The tapered surfaces involved at 28 and 18 are also less than the angle of friction, eliminating possibility of chatter. The blades are held against relative rotational movement by the tapered surfaces of the driving lugs and depressions. The stem imparts torque through the threads 12 to the pin, and the pin through the hexagonal section 14 to the driving collar 22. Although the driving angle at this non-round portion will not necessarily be less than the angle of friction, or repose, for the metals involved, chatter does not occur at this point because the metals are not subject to the strains which are involved at the blades themselves. The blades themselves are cantilevers and therefore considerable strain occurs.

By driving from the outside surface of the holding portion 36 of the blades, less force is required for a given torque. If the blades were driven from the pin 14, the radius to the driving lug would be less and consequently a greater force necessary for the same torque.

Removal of the blades is facilitated by the wedge type drive. When in use, the rotational torque will cause the blades to ride back on lugs 29 so that there is a gap be tween the trailing face 39 of the lugs and the corresponding portion of the blade as seen in FIG. 3. When it is desired to remove the blades from the holder, the first step is to strike the back face 42 of the blades a sharp blow. This impact will rotate the blades relative to the collar. This initial movement will move the lugs fully into the depression, i.e., drive the blades ofi the wedge. 'I his slight movement will remove most of the strain from the collar, making rotation of the collar easier.

It will be apparent that the embodiment shown is only exemplary and that various modifications can be made in construction, materials, and arrangement within the scope of the invention as defined in the appended claims.

I claim as my invention:

1. A drilling bit for attachment to a tubular stern comprising: a tubular pin of generally circular cross-section, external screw threads on the upper end of the pin, the lower end of the pin having an annular groove, a collar co-axial with the pin, means for rotating the collar with the pin, a plurality of drilling blades, each blade having a drilling face and back face, each blade having a holding portion between the collar and the pin and contacting each, a flange on the holding portion correlative with and contacting said groove, a plurality of driving lugs on the internal surface of said collar, said lugs appearing as wedges on a plane normal to the axis of the pin intersecting the bit, and a depression on each blade correlative with and contacting its corresponding lug, said depression sloping back and in from a direction of the drilling face to the back face of the blade, the angle of slope of said depressions being less than the friction angle for the materials of the blade and collar, so that the blade is driven by a wedge surface the slope angle of which is less than the angle of friction.

2. A drilling bit comprising: a tubular pin, co-axial threads on one end of the pin so that it is adapted to be screwed onto a supporting drill stem, an external annular groove near the other end of the pin, an external section of the pin between the threads and groove being nonround; a collar surrounding a portion of the pin co-axial therewith, an internal portion of the collar being nonround which portion mates the non-round section of the pin, wedge shaped lugs on an internal portion of the collar; and a plurality of blades, each blade having a holding portion, said holding portion within an annular space between the pin and the collar and contacting each, each blade having a tooth portion which extends outward and is adapted to drill in the earth, said holding portion having a flange which fits in the external annular groove of the pin, said holding portion also having a depression which contacts and is correlative with one of the lugs of the collar.

3. The invention as defined in claim 2 wherein the tooth portion of each blade has a drilling face and back face, and said wedges slope back in a direction from the drilling face to back face, said slope being less than the angle of friction for the materials involved.

4. The invention as defined in claim 2 wherein said non-round portion is hexagonal.

References Cited in the file of this patent UNITED STATES PATENTS 2,615,684 Hawthorne Oct. 28, 1-952 2,656,153 White Oct. 20, 1953 2,666,622 Hawthorne Ian. 19, 1954 2,783,973 Hawthorne et al Mar. 5, 1957 2,831,657 Hawthorne Apr. 22, 1958 

